Can chelation be important in the antiviral activity of isatin β-thiosemicarbazones?

The stability constants of 5-sulfonatoisatin β-thiosemicarbazone (β-thiosemicarbazonoisatin-5- sulfonate) [sibt,(3)] with Zn2+ and Fe2+ have been determined from slow pH titrations (I 0.15M KNO3, 37�). At pH 7.4, the conditional stability constants for the sibt complexes are logK1' 4.5 (Zn2+), 3.1 (Fe2+) and log β2' 8.9 (Zn2+), 6.5 (Fe2+). The mixed ligand complexes Zn(sibt)L (L = histidine or glycine) have conditional stability constants log β1110' 8.8 and 7.0, respectively, at pH 7.4. Copper(I) complexes of sibt and bishistidinato-copper(II) coexist in mixtures of Cu2+, sibt and histidine. [In solutions of copper ions, sibt (complexes Cu+) and histidine (chelates Cu2+), the response of the Orion cupric-ion-selective electrode is not stoichiometric.] Also studied was 1-methyl-5-sulfonatoisatin β-thiosemicarbazone [msibt,(4)] which behaves like sibt. 5-Sulfonatoisatin β-semicarbazone and p-sulfonatobenzaldehyde thiosemicarbazone (p-thiosemicarbazonomethyl- benzenesulfonate) are weak ligands. Comparison of the stability constants with those of complexes of biologically relevant chelating agents showed that isatin β-thiosemicarbazones are not expected to form stable complexes with zinc and iron in vivo. Bidentate thiosemicarbazones, such as benzaldehyde thiosemicarbazones, form even weaker complexes. Both classes of thiosernicarbazones have a similar activity against vaccinia virus; this activity seems not to depend on metal ion chelation.

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Copper complexation by isatin β-thiosemicarbazones in aqueous solution

Australian Journal of Chemistry ◽

10.1071/ch9812549 ◽

1981 ◽

Vol 34 (12) ◽

pp. 2549 ◽

Cited By ~ 8

Author(s):

H Stunzi

Keyword(s):

Aqueous Solution ◽

Stability Constants ◽

Antiviral Drug ◽

Copper Electrode ◽

Water Soluble ◽

Conditional Stability ◽

Cupric Ion ◽

Copper Complexation ◽

The Stability

The reactions in aqueous solution between cupric ion and water-soluble derivatives of the antiviral drug methisazone (1-methylisatin β-thiosemicarbazone, mibt) have been investigated. Alkalimetric titrations and n.m.r. experiments showed that 5-sulfonatoisatin β-thiosemicarbazone, sibt (3), its 1-methyl derivative, msibt (4), and also p-sulfonatobenzaldehyde thiosemicarbazone, sbat (5), reduce cupric ion and form copper(I) complexes. Stability constants were obtained from measurements of pH and pCu+ on solutions of copper(II) nitrate and excess ligand (I = 0.15 M KNO3, at 37�). The pCu+ values were obtained with an ORION solid state copper electrode. At pH 6-7.5 and moderate excess of ligand, polymeric complexes with an approximate 1 : 1 copper(1)-to-ligand ratio are formed: CunLn or CunLn+,H with n > 6. Monomeric complexes CuL23- predominate at higher pH and in the presence of a more than twentyfold excess of ligand. The stability constants log β2 are 17.9 for sibt, 18.5 for msibt and 19.8 for sbat. At physiological pH (7.4), the order of stability is msibt > sibt & sbat, with conditional stability constants log β2 = 16.2, 15.7 and 13.4, respectively. Comparison with penicillamine shows that some in vivo complexation of copper(I) by methisazone may be possible. On the other hand, a histidinato-copper(II) complex is formed in the presence of histidine.

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Fluorescence Analysis of Cu(II), Pb(II) and Hg(II) Ion Binding to Humic and Fulvic Acids

Materials Science Forum ◽

10.4028/www.scientific.net/msf.851.135 ◽

2016 ◽

Vol 851 ◽

pp. 135-140 ◽

Cited By ~ 3

Author(s):

Vojtěch Enev ◽

Irena Türkeová ◽

Jana Szewieczková ◽

Leos Doskocil ◽

Martina Klučáková

Keyword(s):

Humic Substances ◽

Stability Constants ◽

Metal Ion ◽

Fluorescence Analysis ◽

Fulvic Acids ◽

Ion Binding ◽

Conditional Stability ◽

Metal Ion Binding ◽

The Stability ◽

Conditional Stability Constants

Abstract. The aim of this work was to study molecular and quantitative aspects of metal ion binding to humic substances (HS). The object of our study was characterization of two standards of humic substances (Elliott Soil standard HA 1S102H and Elliott Soil standard FA 2S102F). All samples of IHSS standards HS were characterized by elemental analysis (EA), ultraviolet-visible spectroscopy (UV/Vis), Fourier transform infrared spectroscopy (FTIR) and steady-state fluorescence spectroscopy. Chemical parameters on the complexation of Cu (II), Pb(II) and Hg(II), including the conditional stability constants and the percentage of fluorophores participating in the complexation, were estimated by the modified Stern–Volmer equation. The stability constants (log Ka) of Me(II)–ESHS complexes range from 3.70 to 5.15 in the order: Hg–ESHA>Cu–ESHA>Pb–ESHA>Cu–ESFA>Pb–ESFA. With respect to the ESHA, ESFA, which showed the smallest contents of O-containing functional groups (e.g. hydroxyl, carbonyl, ester, especially carboxyl groups on the aromatic ring) and the lowest humification degree, the ESFA was characterized by much smaller stability constants. Our findings suggest that soil HS belongs to class of important organic ligands for complexation with heavy metal ions and may significantly affect the chemical forms, mobility, bioavailability and ecotoxicity of heavy metals in the soil environment.

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The Extraction of Anionic Beryllium Complexes by Tri-iso-octylamine

Australian Journal of Chemistry ◽

10.1071/ch9620457 ◽

1962 ◽

Vol 15 (3) ◽

pp. 457 ◽

Cited By ~ 27

Author(s):

HJ de Bruin ◽

D Kairaitis ◽

RB Temple

Keyword(s):

Aqueous Solution ◽

Stability Constants ◽

Complexing Agents ◽

Conditional Stability ◽

Tertiary Amines ◽

Ph Titration ◽

Anionic Complexes ◽

The Stability ◽

Conditional Stability Constants ◽

Beryllium Complexes

The extraction of beryllium from aqueous solution by long-chain tertiary amines has been observed in the presence of ligands giving rise to anionic complexes. The nature of the oxalate complex extracted by solutions of tri-iso-octylamine in chloroform has been studied in detail and the species formed in the organic phase were shown to have the composition Be(C2O4)2.{NH(i-C8H15)3}2. The complexes formed in aqueous solution between beryllium and several anionic complexing agents have been examined by the method of pH-titration. Conditional stability constants have been obtained for the complexes formed with oxalic, malonic, maleic, succinic, phthalic, and salicylic acids. Differences in their extractabilities can be explained semiquantitatively with the help of the stability constants and the acid association constants of the complexing agents.

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Metal Ion Coordination, Conditional Stability Constants, and Solution Behavior of Chelating Surfactant Metal Complexes

Langmuir ◽

10.1021/la5002336 ◽

2014 ◽

Vol 30 (16) ◽

pp. 4605-4612 ◽

Cited By ~ 20

Author(s):

Ida Svanedal ◽

Susanne Boija ◽

Ann Almesåker ◽

Gerd Persson ◽

Fredrik Andersson ◽

...

Keyword(s):

Metal Complexes ◽

Stability Constants ◽

Metal Ion ◽

Conditional Stability ◽

Solution Behavior ◽

Conditional Stability Constants

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8-Hydroxyquinoline Glycoconjugates Containing Sulfur at the Sugar Anomeric Position—Synthesis and Preliminary Evaluation of Their Cytotoxicity

Molecules ◽

10.3390/molecules25184174 ◽

2020 ◽

Vol 25 (18) ◽

pp. 4174 ◽

Cited By ~ 1

Author(s):

Monika Krawczyk ◽

Gabriela Pastuch-Gawołek ◽

Agnieszka Hadasik ◽

Karol Erfurt

Keyword(s):

Cancer Cells ◽

Metal Ion ◽

Copper Ions ◽

Preliminary Evaluation ◽

Hydrolytic Cleavage ◽

The Stability ◽

Position Synthesis ◽

New Compounds ◽

Metal Ion Chelation ◽

Mcf 7

One of the main factors limiting the effectiveness of many drugs is the difficulty of their delivery to their target site in the cell and achieving the desired therapeutic dose. Moreover, the accumulation of the drug in healthy tissue can lead to serious side effects. The way to improve the selectivity of a drug to the cancer cells seems to be its conjugation with a sugar molecule, which should facilitate its selective transport through GLUT transporters (glucose transporters), whose overexpression is seen in some types of cancer. This was the idea behind the synthesis of 8-hydroxyquinoline (8-HQ) derivative glycoconjugates, for which 1-thiosugar derivatives were used as sugar moiety donors. It was expected that the introduction of a sulfur atom instead of an oxygen atom into the anomeric position of the sugar would increase the stability of the obtained glycoconjugates against untimely hydrolytic cleavage. The anticancer activity of new compounds was determined based on the results of the MTT cytotoxicity tests. Because of the assumption that the activity of this type of compounds was based on metal ion chelation, the effect of the addition of copper ions on cell proliferation was tested for some of them. It turned out that cancer cells treated with glycoconjugates in the presence of Cu2+ had a much slower growth rate compared to cells treated with free glycoconjugates in the absence of copper. The highest cytotoxic activity of the compounds was observed against the MCF-7 cell line.

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Conditional Stability Constants for Copper Ions with Ligands in Natural Waters

ACS Symposium Series - Chemical Modeling in Aqueous Systems ◽

10.1021/bk-1979-0093.ch006 ◽

1979 ◽

pp. 115-132 ◽

Cited By ~ 10

Author(s):

CONSTANT M. G. VAN DEN BERG ◽

JAMES R. KRAMER

Keyword(s):

Stability Constants ◽

Natural Waters ◽

Copper Ions ◽

Conditional Stability ◽

Conditional Stability Constants

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Studies on the Coordination Reaction of VO2+ and Tannic Acid in the Tannin Extract Desulfurization

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.239-240.1573 ◽

2012 ◽

Vol 239-240 ◽

pp. 1573-1576

Author(s):

Zhu Qing Gao ◽

Xiao Dong Cai ◽

Kai Cheng Ling

Keyword(s):

Stability Constants ◽

Tannic Acid ◽

Ph Value ◽

Protonation Constants ◽

Conditional Stability ◽

Tannin Extract ◽

Acid Effect ◽

Different Temperatures ◽

The Stability ◽

Apparent Stability

At different temperatures, the protonation constants of tannic acid and the complex apparent stability constants between tannic acid and VO2+ were determined by using pH potentimetric method. The results showed that the protonation constants and the complex apparent stability constants slightly decreased with the raising temperature. In accordance with the pH value in the tannin extract technology, the conditional stability constants of the complex were calculated on the basis of the acid effect of tannic acid and the hydrolysis effect of VO2+. It was found that pH greatly affected the stability constants of the complex , so pH must be strictly controlled in the tannin extract technology.

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